1. Field of the Invention
This invention broadly relates to intra-oral appliances that are used during the course of orthodontic treatment. More particularly, the present invention relates to self-ligating orthodontic appliances having one or more clips for releasably retaining an archwire in an archwire slot of the appliance.
2. Description of the Related Art
Orthodontic therapy is a specialized type of treatment within the field of dentistry, and involves of repositioning of malpositioned teeth to orthodontically correct locations. Orthodontic therapy often enhances the aesthetic appearance of the teeth, especially in instances when the patient's front teeth are malpositioned or crooked. Orthodontic treatment can also improve the patient's occlusion so that opposed teeth function better with each other during the times that the patient is chewing.
Many types of orthodontic treatment programs involve the use of a set of tiny appliances and archwires that are commonly known collectively as “braces”. During such treatment programs, small appliances known as brackets are fixed to the patient's anterior, cuspid and bicuspid teeth, and an archwire is inserted into a slot of each bracket. The archwire forms a track to guide movement of the teeth to desired positions. End sections of the archwires are often captured in tiny appliances known as buccal tubes that are fixed to the patient's molar teeth.
Many orthodontic brackets have small wings known as “tiewings” that are connected to a body of the bracket. Once the bracket has been attached to a tooth and an archwire has been placed in the archwire slot of the bracket, a ligature is coupled to the bracket in order to retain the archwire in the archwire slot. One example of a commercially available orthodontic ligature is a small, elastomeric O-ring that is installed by stretching the O-ring along a path behind the tiewings and over the facial side of the archwire.
Other types of orthodontic appliances are known as self-ligating brackets, and are provided with a latch for coupling the archwire to the bracket. Use of the latch avoids the need to use a ligature to secure the archwire to the bracket. The latch may comprise a movable clip, spring member, sliding cover, shutter, bail or other structure that is connected to the bracket body for retaining the archwire in the archwire slot.
Examples of improved, self-ligating orthodontic appliances with clips are described in applicant's U.S. Pat. Nos. 6,582,226, 7,140,876, and 7,217,125 and 7,377,777. The appliances described in those documents have one or more clips for retaining an archwire in the archwire slot, and the clips release the archwire from the archwire slot whenever the archwire exerts a force on the appliance that exceeds a certain minimum value. The minimum value is significantly less than the force required in the same direction to debond the appliance from the tooth, and consequently helps to ensure that the appliance will not spontaneously debond from the tooth during the course of treatment.
U.S. Pat. No. 6,776,614 describes a system of customized orthodontic brackets and archwires. This patent further describes designing the brackets on a computer as a combination of three-dimensional virtual objects including a virtual bracket bonding pad and a virtual bracket body retrieved from a library of virtual bracket bodies. The virtual brackets can be represented as a file containing digital shape data that can be exported to a rapid prototype fabrication device. The rapid prototype fabrication device can be used to make models of the brackets which, in turn, are then used to form molds for subsequent casting of the brackets.
Orthodontic appliances including brackets having an overall, generally small or low profile are often desired by practitioners for use in treatment. Such low profile appliances are less likely to contact other teeth or appliances in the patient's oral cavity, an important advantage in certain instances when the teeth are not initially positioned in substantial alignment relative to each other. Low profile appliances are also less likely to impinge on the patient's oral tissue and cause irritation of the same.